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Bombs behaving badly: unexpected trajectories and cooling of volcanic projectiles |
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| Authors: | Lo?c Vanderkluysen Andrew J L Harris Karim Kelfoun Costanza Bonadonna Maurizio Ripepe |
| Institution: | 1. Hawai‘i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai‘i, Honolulu, HI, 96822, USA 5. ASU School of Earth and Space Exploration, PO Box 876004, Tempe, AZ, 85287-6004, USA 2. Laboratoire Magmas et Volcans, Université Blaise Pascal, 63038, Clermont-Ferrand, France 3. Section des Sciences de la Terre et de l’Environnement, Université de Genève, 1205, Geneva, Switzerland 4. Dipartimento di Scienze della Terra, Università degli Studi di Firenze, 50121, Florence, Italy |
| Abstract: | We collected thermal infrared video of two explosive eruptions at Stromboli in June 2008 and manually traced the trajectories of 95 particles launched during two eruptions. We found that 10–15?% of the analyzed trajectories deviated from predicted curves due to collisions, causing one particle to travel horizontally more than twice as far as expected. Furthermore, we observed an oscillatory cooling behavior for the airborne pyroclasts, with a median period of 0.46?s. Measured cooling was typically much faster than model-predicted cooling with discrepancies of up to 40?% between measured cooling and theoretical modeling. We interpret the measured cooling curves as resulting from the spinning and twisting and tearing of particles during travel: the periodic re-exposing of the hotter core of the pyroclasts to the atmosphere may cause the observed oscillations, and the spinning may accelerate cooling by enhancing convective heat transfer. Current volcanic trajectory and cooling models do not account for projectile collisions, spinning, or tearing and can thus severely underestimate the maximum landing distance and cooling rates of large pyroclasts. |
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